Japan’s threat that many of its companies will quit the UK if Brexit negotiations are botched comes with an unprecedented and slightly panicky list of demands. The message to London and Brussels is that Tokyo wants certainty from the outset that every effort will be made to keep the UK’s borders open for people, goods and the complex financial transactions that are the lifeblood of modern global capitalism.

In a letter to the EU and UK at the G20 summit in China, Japan says it is representing the needs of businesses that have invested heavily in the UK with a view to exporting across Europe. NIssan’s Washington plant in Sunderland, Tyne and Wear, exports more than 80% of the cars it makes. The new Hitachi train factory down the road in Newton Aycliffe is making trains for the UK, but has ambitions to compete with Germany’s Siemens for contracts across the continent.

Although the letter says Tokyo respects the referendum vote, the clear demand is for the current arrangements to stay the same for businesses to invest and create jobs. At its heart, the letter implies that UK exports could be jeopardised by a Liam Fox- or David Davis-inspired break with the EU that involves the re-introduction of trade barriers and quotas restricting immigration, whatever the secretary of state for international trade (Fox) or secretary of state for exiting the European Union (Davis) says about their plans for signing deals with other countries.

The demands range from the maintenance of low tariffs on exports to keeping various EU agencies in the UK. Some look possible, others almost fanciful. Here we assess the likelihood that the upcoming negotiations can address the concerns of Japanese businesses, beginning with:

Maintenance of the current tariff rates and customs clearance procedures

There is pressure from businesses on both sides of the channel to keep tariffs on goods low and allow lorries to zip back and forth without hindrance. It’s possible the French and German governments will accede to giving the UK special privileges to please Volkswagen and Renault – which owns 43% of Nissan – as much as UK exporters concerned at the potential loss of trade.

Theresa May joins G20 summit to face Brexit warnings from US and Japan

Read more

Maintenance of the access to workers who are nationals of the UK or the EU

It seems likely the Conservative government will adopt a points-based immigration system that will favour skilled workers, alleviating the concerns of Japanese employers at the loss of unfettered access to EU nationals.

Maintenance of the freedom of establishment and the provision of financial services, including the “single passport” system

UK banks and insurance companies can process transactions without any barriers while they remain part of the EU. The National Institute for Economic & Social Research has said the loss of passporting rights for financial services companies will be a huge blow for London.

Maintenance of the freedom of cross-border investment and the provision of services as well as the free movement of capital, including that between associated companies

London plays host to the financial businesses that process most transactions in euros, to the resentment of Frankfurt and Paris. Appeals to the European court of justice are expected post-Brexit from continental financial centres, seeking to bring all euro transactions with the EU. Most likely they will succeed, robbing London of an important resource.

Location within the UK of EU agencies such as the European Medicines Agency (EMA) and the maintenance of the UK’s access to the EU budget for research and development and participation in the Japan-EU joint research project

Both these requests are almost certain to be denied. Without a doubt, Brussels will pull back all its agencies to inside the EU, probably encouraged by Japan’s statement that its London-based pharmaceutical companies would shift their headquarters across the channel if this happened.

Maintenance of basic policies regarding the entry of foreign capital and implementation of measures to promote investment

There are unlikely to be any barriers put up by the government against foreign investment post-Brexit. If anything, the incentives are likely to increase once EU state-aid rules preventing the UK from subsidising business investment no longer apply.

Ensuring the consistency of regulations and standards between the UK and the EU

Exporters appreciate harmonised regulations, and initially little is expected to change. There will be demands for the UK to develop its own rules, especially when signing trade deals with countries outside the EU, in areas like agriculture. Ditching the ban on GM foods is first on many farmers’ lists.

• This article was amended on 5 September 2016. An earlier version placed Nissan’s Washington plant in County Durham.